Curiosity was launched from Cape Canaveral on November 26, 2011, at 10:02 EST aboard the MSL spacecraft and landed on Aeolis Palus in Gale Crater on Mars on August 6, 2012, 05:17 UTC.[1][11] The Bradbury Landing site[8] was less than 2.4 km (1.5 mi) from the center of the rover's touchdown target after a 563,000,000 km (350,000,000 mi) journey.[12]

About one year into the surface mission, and having assessed that ancient Mars could have been hospitable to microbial life, the MSL mission objectives evolved to developing predictive models for the preservation process of biomolecules; a branch of paleontology called taphonomy.[19]

Specifications

Curiosity comprised 23 percent of the mass of the 3,893 kg (8,583 lb) Mars Science Laboratory (MSL) spacecraft, which had the sole mission of delivering the rover safely across space from Earth to a soft landing on the surface of Mars. The remaining mass of the MSL craft was discarded in the process of carrying out this task.

Curiosity '​s power generator is the latest RTG generation built by Boeing and Idaho National Laboratory, called the Multi-Mission Radioisotope Thermoelectric Generator or MMRTG.[25][26] Based on legacy RTG technology, it represents a more flexible and compact development step,[25] and is designed to produce 125 watts of electrical power from about 2,000 watts of thermal power at the start of the mission.[22][23] The MMRTG produces less power over time as its plutonium fuel decays: at its minimum lifetime of 14 years, electrical power output is down to 100 watts.[27][28] The power source will generate 9 MJ (2.5 kWh) each day, much more than the solar panels of the Mars Exploration Rovers, which can generate about 2.1 MJ (0.58 kWh) each day. The electrical output from the MMRTG charges two rechargeable lithium-ion batteries. This enables the power subsystem to meet peak power demands of rover activities when the demand temporarily exceeds the generator’s steady output level. Each battery has a capacity of about 42 amp-hours.

Heat rejection system: The temperatures at the landing site can vary from −127 to 40 °C (−197 to 104 °F); therefore, the thermal system will warm the rover for most of the Martian year. The thermal system will do so in several ways: passively, through the dissipation to internal components; by electrical heaters strategically placed on key components; and by using the rover heat rejection system (HRS).[29] It uses fluid pumped through 60 m (200 ft) of tubing in the rover body so that sensitive components are kept at optimal temperatures.[30] The fluid loop serves the additional purpose of rejecting heat when the rover has become too warm, and it can also gather waste heat from the power source by pumping fluid through two heat exchangers that are mounted alongside the RTG. The HRS also has the ability to cool components if necessary.[30]

Computers: The two identical on-board rover computers, called Rover Computer Element (RCE) contain radiation hardened memory to tolerate the extreme radiation from space and to safeguard against power-off cycles. Each computer's memory includes 256 kB of EEPROM, 256 MB of DRAM, and 2 GB of flash memory.[31] Compare these figures to the 3 MB of EEPROM, 128 MB of DRAM, and 256 MB of flash memory used in the Mars Exploration Rovers.[32]

The RCE computers use the RAD750CPU, which is a successor to the RAD6000 CPU of the Mars Exploration Rovers.[33][34] The RAD750 CPU can execute up to 400 MIPS, while the RAD6000 CPU is capable of up to only 35 MIPS.[35][36] Of the two on-board computers, one is configured as backup and will take over in the event of problems with the main computer.[31] On February 28, 2013, NASA was forced to switch to the backup computer due to an issue with the then active computer's flash memory, which resulted in the computer continuously rebooting in a loop. The backup computer was turned on in safe mode and subsequently returned to active status on March 4.[37] The same issue happened in late March, resuming full operations on March 25, 2013.[38]

The rover has an Inertial Measurement Unit (IMU) that provides 3-axis information on its position, which is used in rover navigation.[31] The rover's computers are constantly self-monitoring to keep the rover operational, such as by regulating the rover's temperature.[31] Activities such as taking pictures, driving, and operating the instruments are performed in a command sequence that is sent from the flight team to the rover.[31] The rover installed its full surface operations software after the landing because its computers did not have room for it during flight. The new software essentially replaced the flight software.[12]

Curiosity transmits to Earth directly or via three relay satellites in Mars orbit.

Communications: Curiosity is equipped with significant telecommunication redundancy by several means – an X bandtransmitter and receiver that can communicate directly with Earth, and a UHF Electra-Lite software-defined radio for communicating with Mars orbiters.[29] Communication with orbiters is expected to be the main path for data return to Earth, since the orbiters have both more power and larger antennas than the lander allowing for faster transmission speeds.[29] Telecommunication includes a small deep space transponder on the descent stage and a solid-state power amplifier on the rover for X band. The rover also has two UHF radios,[29] the signals of which the 2001 Mars Odyssey satellite is capable of relaying back to Earth. An average of 14 minutes, 6 seconds will be required for signals to travel between Earth and Mars.[39]Curiosity can communicate with Earth directly at speeds up to 32 kbit/s, but the bulk of the data transfer should be relayed through the Mars Reconnaissance Orbiter and Odyssey orbiter. Data transfer speeds between Curiosity and each orbiter may reach 2 Mbit/s and 256 kbit/s, respectively, but each orbiter is only able to communicate with Curiosity for about eight minutes per day (0.56% of the time).[40] Communication from and to Curiosity relies on internationally-agreed space data communications protocols as defined by the Consultative Committee for Space Data Systems.[41]

JPL is the central data distribution hub where selected data products are provided to remote science operations sites as needed. JPL is also the central hub for the uplink process, though participants are distributed at their respective home institutions.[29] At landing, telemetry was monitored by three orbiters, depending on their dynamic location: the 2001 Mars Odyssey, Mars Reconnaissance Orbiter and ESA's Mars Express satellite.[42]

Mobility systems: Curiosity is equipped with six 50 cm (20 in) diameter wheels in a rocker-bogie suspension. The suspension system also served as landing gear for the vehicle, unlike its smaller predecessors.[43][44] Each wheel has cleats and is independently actuated and geared, providing for climbing in soft sand and scrambling over rocks. Each front and rear wheel can be independently steered, allowing the vehicle to turn in place as well as execute arcing turns.[29] Each wheel has a pattern that helps it maintain traction but also leaves patterned tracks in the sandy surface of Mars. That pattern is used by on-board cameras to judge the distance traveled. The pattern itself is Morse code for "JPL" (·--- ·--· ·-··).[45] The rover is capable of climbing sand dunes with slopes up to 12.5°.[46] Based on the center of mass, the vehicle can withstand a tilt of at least 50° in any direction without overturning, but automatic sensors will limit the rover from exceeding 30° tilts.[29] After two years of use, the wheels are visibly worn with punctures and tears.[47]

Curiosity can roll over obstacles approaching 65 cm (26 in) in height,[48] and it has a ground clearance of 60 cm (24 in).[49] Based on variables including power levels, terrain difficulty, slippage and visibility, the maximum terrain-traverse speed is estimated to be 200 m (660 ft) per day by automatic navigation.[48] The rover landed about 10 km (6.2 mi) from the base of Mount Sharp,[50] and it is expected to traverse a minimum of 19 km (12 mi) during its primary two-year mission.[51] It can travel up to 90 metres (300 ft) per hour but average speed is about 30 metres (98 ft) per hour.[51]

Instruments

Instrument location diagram

The general sample analysis strategy begins with high-resolution cameras to look for features of interest. If a particular surface is of interest, Curiosity can vaporize a small portion of it with an infrared laser and examine the resulting spectra signature to query the rock's elemental composition. If that signature is intriguing, the rover will use its long arm to swing over a microscope and an X-ray spectrometer to take a closer look. If the specimen warrants further analysis, Curiosity can drill into the boulder and deliver a powdered sample to either the SAM or the CheMin analytical laboratories inside the rover.[52][53][54][55] The MastCam, Mars Hand Lens Imager (MAHLI), and Mars Descent Imager (MARDI) cameras were developed by Malin Space Science Systems and they all share common design components, such as on-board electronic imaging processing boxes, 1600×1200 CCDs, and an RGB Bayer pattern filter.[56][57][58][59][60][61]

Mast Camera (MastCam)

The MastCam system provides multiple spectra and true-color imaging with two cameras.[57] The cameras can take true-color images at 1600×1200 pixels and up to 10 frames per second hardware-compressed, video at 720p (1280×720).

The turret at the end of the robotic arm holds five devices

One MastCam camera is the Medium Angle Camera (MAC), which has a 34 mm (1.3 in) focal length, a 15° field of view, and can yield 22 cm/pixel (8.7 in/pixel) scale at 1 km (0.62 mi). The other camera in the MastCam is the Narrow Angle Camera (NAC), which has a 100 mm (3.9 in) focal length, a 5.1° field of view, and can yield 7.4 cm/pixel (2.9 in/pixel) scale at 1 km (0.62 mi).[57] Malin also developed a pair of MastCams with zoom lenses,[62] but these were not included in the rover because of the time required to test the new hardware and the looming November 2011 launch date.[63]

Each camera has eight gigabytes of flash memory, which is capable of storing over 5,500 raw images, and can apply real time lossless data compression.[57] The cameras have an autofocus capability that allows them to focus on objects from 2.1 m (6 ft 11 in) to infinity.[60] In addition to the fixed RGBGBayer pattern filter, each camera has an eight-position filter wheel. While the Bayer filter reduces visible light throughput, all three colors are mostly transparent at wavelengths longer than 700 nm, and have minimal effect on such infrared observations.[57]

Chemistry and Camera complex (ChemCam)

The internal spectrometer (left) and the laser telescope (right) for the mast

ChemCam is a suite of remote sensing instruments, and as the name implies, ChemCam is actually two different instruments combined as one: a laser-induced breakdown spectroscopy (LIBS) and a Remote Micro Imager (RMI) telescope. The ChemCam instrument suite was developed by the French CESR laboratory and the Los Alamos National Laboratory .[64][65][66] The flight model of the mast unit was delivered from the French CNES to Los Alamos National Laboratory.[67] The purpose of the LIBS instrument is to provide elemental compositions of rock and soil, while the RMI will give ChemCam scientists high-resolution images of the sampling areas of the rocks and soil that LIBS targets.[64][68] The LIBS instrument can target a rock or soil sample from up to 7 m (23 ft) away, vaporizing a small amount of it with about 50 to 75 5-nanosecond pulses from a 1067 nminfrared laser and then observing the spectrum of the light emitted by the vaporized rock.

ChemCam has the ability to record up to 6,144 different wavelengths of ultraviolet, visible, and infrared light.[69] Detection of the ball of luminous plasma will be done in the visible, near-UV and near-infrared ranges, between 240 nm and 800 nm.[64] The first initial laser testing of the ChemCam by Curiosity on Mars was performed on a rock, N165 ("Coronation" rock), near Bradbury Landing on August 19, 2012.[70][71][72] The ChemCam team expects to take approximately one dozen compositional measurements of rocks per day.[73]

Using the same collection optics, the RMI provides context images of the LIBS analysis spots. The RMI resolves 1 mm (0.039 in) objects at 10 m (33 ft) distance, and has a field of view covering 20 cm (7.9 in) at that distance.[64]

Navigation cameras (navcams)

First full resolution navcam images

Curiosity '​s self-portrait shows the deck of the rover as viewed from the navcams

Rover Environmental Monitoring Station (REMS)

REMS comprises instruments to measure the Mars environment: humidity, pressure, temperatures, wind speeds, and ultraviolet radiation.[77] It is a meteorological package that includes an ultraviolet sensor provided by the Spanish Ministry of Education and Science. The investigative team is led by Javier Gómez-Elvira of the Center for Astrobiology (Madrid) and includes the Finnish Meteorological Institute as a partner.[78][79] All sensors are located around three elements: two booms attached to the rover's mast, the Ultraviolet Sensor (UVS) assembly located on the rover top deck, and the Instrument Control Unit (ICU) inside the rover body. REMS will provide new clues about the Martian general circulation, micro scale weather systems, local hydrological cycle, destructive potential of UV radiation, and subsurface habitability based on ground-atmosphere interaction.[78]

Hazard avoidance cameras (hazcams)

The rover has four pairs of black and white navigation cameras called hazcams—two pairs in the front and two pairs in the back.[74][80] They are used for autonomous hazard avoidance during rover drives and for safe positioning of the robotic arm on rocks and soils.[80] Each camera in a pair is hardlinked to one of two identical main computers for redundancy; only four out of the eight cameras are in use at any one time. The cameras use visible light to capture stereoscopic three-dimensional (3-D) imagery.[80] The cameras have a 120° field of view and map the terrain at up to 3 m (9.8 ft) in front of the rover.[80] This imagery safeguards against the rover crashing into unexpected obstacles, and works in tandem with software that allows the rover to make its own safety choices.[80]

Mars Hand Lens Imager (MAHLI)

MAHLI is a camera on the rover's robotic arm, and acquires microscopic images of rock and soil. MAHLI can take true-color images at 1600×1200 pixels with a resolution as high as 14.5 micrometers per pixel. MAHLI has an 18.3 to 21.3 mm (0.72 to 0.84 in) focal length and a 33.8–38.5° field of view.[58] MAHLI has both white and ultraviolet LED illumination for imaging in darkness or fluorescence imaging. MAHLI also has mechanical focusing in a range from infinite to millimetre distances.[58] This system can make some images with focus stacking processing.[81] MAHLI can store either the raw images or do real time lossless predictive or JPEG compression. The calibration target for MAHLI includes color references, a metric bar graphic, a 1909 VDB Lincoln penny, and a stairstep pattern for depth calibration.[82]

CheMin is the Chemistry and Mineralogy X-raypowder diffraction and fluorescence instrument.[87] CheMin is one of four spectrometers. It can identify and quantify the abundance of the minerals on Mars. It was developed by David Blake at NASA Ames Research Center and the Jet Propulsion Laboratory,[88] and won the 2013 NASA Government Invention of the year award.[89] The rover can drill samples from rocks and the resulting fine powder is poured into the instrument via a sample inlet tube on the top of the vehicle. A beam of X-rays is then directed at the powder and the crystal structure of the minerals deflects it at characteristic angles, allowing scientists to identify the minerals being analyzed.

Dust Removal Tool (DRT)

The Dust Removal Tool (DRT) is a motorized, wire-bristle brush on the turret at the end of Curiosity '​s arm. The DRT was first used on a rock target named Ekwir 1 on January 6, 2013. Honeybee Robotics built the DRT.

Radiation assessment detector (RAD)

This instrument was the first of ten MSL instruments to be turned on. Its first role was to characterize the broad spectrum of radiation environment found inside the spacecraft during the cruise phase. These measurements have never been done before from the inside of a spacecraft in interplanetary space. Its primary purpose is to determine the viability and shielding needs for potential human explorers, as well as to characterize the radiation environment on the surface of Mars, which it started doing immediately after MSL landed in August 2012.[97] Funded by the Exploration Systems Mission Directorate at NASA Headquarters and Germany's Space Agency (DLR), RAD was developed by Southwest Research Institute (SwRI) and the extraterrestrial physics group at Christian-Albrechts-Universität zu Kiel, Germany.[97][98]

Mars Descent Imager (MARDI)

MARDI camera

During the descent to the Martian surface, MARDI took color images at 1600×1200 pixels with a 1.3-millisecond exposure time starting at distances of about 3.7 km (2.3 mi) to near 5 m (16 ft) from the ground, at a rate of four frames per second for about two minutes.[59][103] MARDI has a pixel scale of 1.5 m (4.9 ft) at 2 km (1.2 mi) to 1.5 mm (0.059 in) at 2 m (6.6 ft) and has a 90° circular field of view. MARDI has eight gigabytes of internal buffer memory that is capable of storing over 4,000 raw images. MARDI imaging allowed the mapping of surrounding terrain and the location of landing.[59]JunoCam, built for the Juno spacecraft, is based on MARDI.[104]

Robotic arm

The rover has a 2.1 m (6.9 ft) long arm with a cross-shaped turret holding five devices that can spin through a 350° turning range.[106][107] The arm makes use of three joints to extend it forward and to stow it again while driving. It has a mass of 30 kg (66 lb) and its diameter, including the tools mounted on it, is about 60 cm (24 in).[108]

Two of the five devices are in-situ or contact instruments known as the X-ray spectrometer (APXS), and the Mars Hand Lens Imager (MAHLI camera). The remaining three are associated with sample acquisition and sample preparation functions: a percussion drill, a brush, and mechanisms for scooping, sieving and portioning samples of powdered rock and soil.[106][108] The diameter of the hole in a rock after drilling is 1.6 cm (0.63 in) and up to 5 cm (2.0 in) deep.[107][109] The drill carries two spare bits.[109][110] The rover's arm and turret system can place the APXS and MAHLI on their respective targets, and also obtain powdered sample from rock interiors, and deliver them to the SAM and CheMin analyzers inside the rover.[107]

Comparisons

Two Jet Propulsion Laboratory engineers stand with three vehicles, providing a size comparison of three generations of Mars rovers. Front and center is the flight spare for the first Mars rover, Sojourner, which landed on Mars in 1997 as part of the Mars Pathfinder Project. On the left is a Mars Exploration Rover (MER) test vehicle that is a working sibling to Spirit and Opportunity, which landed on Mars in 2004. On the right is a test rover for the Mars Science Laboratory, which landed Curiosity on Mars in 2012. Sojourner is 65 cm (2.13 ft) long. The Mars Exploration Rovers (MER) are 1.6 m (5.2 ft) long. Curiosity on the right is 3 m (9.8 ft) long.

Curiosity is 2.9 m (9.5 ft) long by 2.7 m (8.9 ft) wide by 2.2 m (7.2 ft) in height,[21] larger than Mars Exploration Rovers, which are 1.5 m (4.9 ft) long and have a mass of 174 kg (384 lb) including 6.8 kg (15 lb) of scientific instruments.[20][111][112] In comparison to Pancam on the Mars Exploration Rovers, the MastCam-34 has 1.25× higher spatial resolution and the MastCam-100 has 3.67× higher spatial resolution.[60]

The leader of the Beagle 2 project reacted emotionally to the large number of technicians monitoring Curiosity '​s descent, because the Beagle 2 had only had four people monitoring it.[115] The Beagle 2 team made a virtue out of necessity; it was known that there was no chance of obtaining funds in Europe, at that time, of the scale previously considered necessary for a Mars rover, so the team used innovative methods to reduce the cost to less than 4% of the cost of the Curiosity mission. They also only had one shot, with no funding for repeat missions (it was named Beagle 2 as a successor to HMS Beagle, not to an earlier rover). It was considered a large risk, and Beagle 2 did not survive its landing.[115] The team have proposed that a future launch might take multiple low-cost Beagle-type landers, with a realistic expectation that the vast majority would be successful, allowing exploration of several parts of Mars and possibly asteroids, all for considerably less cost than a single "normal" rover expedition. [116]

Landing

Landing site

Curiosity landed in Quad 51 (nicknamed Yellowknife) of Aeolis Palus in Gale Crater.[117][118][119][120] The landing site coordinates are: .[9][10] The location has been named Bradbury Landing in honor of science fiction author Ray Bradbury.[8] Gale crater, an estimated 3.5 to 3.8 billion-year-old impact crater, is hypothesized to have first been gradually filled in by sediments; first water-deposited, and then wind-deposited, possibly until it was completely covered. Wind erosion then scoured out the sediments, leaving an isolated 5.5 km (3.4 mi) high mountain, Aeolis Mons ("Mount Sharp"), at the center of the 154 km (96 mi) wide crater. Thus, it is believed that the rover may have the opportunity to study two billion years of Martian history in the sediments exposed in the mountain. Additionally, its landing site is near an alluvial fan, which is hypothesized to be the result of a flow of ground water, either before the deposition of the eroded sediments or else in relatively recent geologic history.[121][122]

Rover role in the landing system

NASA video describing the landing procedure. NASA called the landing "the Seven Minutes of Terror".

Previous NASA Mars rovers became active only after the successful entry, descent and landing on the Martian surface. Curiosity, on the other hand, was active when it touched down on the surface of Mars, employing the rover suspension system for the final set-down.[123]

Curiosity transformed from its stowed flight configuration to a landing configuration while the MSL spacecraft simultaneously lowered it beneath the spacecraft descent stage with a 20 m (66 ft) tether from the "sky crane" system to a soft landing—wheels down—on the surface of Mars.[124][125][126][127] After the rover touched down it waited 2 seconds to confirm that it was on solid ground then fired several pyros (small explosive devices) activating cable cutters on the bridle to free itself from the spacecraft descent stage. The descent stage then flew away to a crash landing, and the rover prepared itself to begin the science portion of the mission.[128]

Coverage, cultural impact and legacy

Live video showing the first footage from the surface of Mars was available at NASA TV, during the late hours of August 6, 2012 PDT, including interviews with the mission team. The NASA website momentarily became unavailable from the overwhelming number of people visiting it,[130] and a 13-minute NASA excerpt of the landings on its YouTube channel was halted an hour after the landing by a robotic DMCA takedown notice from Scripps Local News, which prevented access for several hours.[131] Around 1,000 people gathered in New York City's Times Square, to watch NASA's live broadcast of Curiosity '​s landing, as footage was being shown on the giant screen.[132]Bobak Ferdowsi, Flight Director for the landing, became an Internet meme and attained Twitter celebrity status, with 45,000 new followers subscribing to his Twitter account, due to his Mohawk hairstyle with yellow stars that he wore during the televised broadcast. [133][134]

On August 13, 2012, U.S. President Barack Obama, calling from aboard Air Force One to congratulate the Curiosity team, said, "You guys are examples of American know-how and ingenuity. It's really an amazing accomplishment."[129] (Video (07:20))

Scientists at the Getty Conservation Institute in Los Angeles, California, viewed the CheMin instrument aboard Curiosity as a potentially valuable means to examine ancient works of art without damaging them. Until recently, only a few instruments were available to determine the composition without cutting out physical samples large enough to potentially damage the artifacts. CheMin directs a beam of X-rays at particles as small as 400 micrometres (0.016 in)[135] and reads the radiationscattered back to determine the composition of the artifact in minutes. Engineers created a smaller, portable version named the X-Duetto. Fitting into a few briefcase-sized boxes, it can examine objects on site, while preserving their physical integrity. It is now being used by Getty scientists to analyze a large collection of museum antiques and the Roman ruins of Herculaneum, Italy.[136]

Prior to the landing, NASA and Microsoft released Mars Rover Landing, a free downloadable game on Xbox Live that uses Kinect to capture body motions, which allows users to simulate the landing sequence.[137]

NASA gave the general public the opportunity from 2009 until 2011 to submit their names to be sent to Mars. More than 1.2 million people from the international community participated, and their names were etched into silicon using an electron-beam machine used for fabricating micro devices at JPL, and this microchip is now installed on the deck of Curiosity.[138] In keeping with a 40-year tradition, a plaque with the signatures of President Barack Obama and Vice President Joe Biden was also installed. Elsewhere on the rover is the autograph of Clara Ma, the 12-year-old girl from Kansas who gave Curiosity its name in an essay contest, writing in part that "curiosity is the passion that drives us through our everyday lives."[139]

On August 6, 2013, Curiosity audibly played "Happy Birthday to You" in honor of the one Earth year mark of its Martian landing, the first time for a song to be played on another planet. This was also the first time music was transmitted between two planets.[140]

Curiosity will serve as the basis for the design of the Mars 2020 rover mission that is presently planned to be launched to Mars in 2020. Some spare parts from the build and ground test of the Curiosity rover may be used in the new vehicle.[141]

Curiosity '​s view of the Rocknest area. South is at center, north is at both ends. Mount Sharp dominates the horizon, while Glenelg is left-of-center and rover tracks are right-of-center (November 16, 2012; white balanced; raw color version; high-res panoramic).

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